The people that say don't use free amps either has someone tuning for them are more equip than the average joe. The average joe doesn't have an analyzer or dyno but he probably has a amp reading device. (DVOM). Also if doing an amp draw between battery and esc, the esc does draw a bit of power. On the order of half amp to 1amp.
As a guy that started with nothing and built up to dyno's, analyzes and stator equipment I can give you this info from an average guy point of view.